Conventionally, a large number of research findings on encoded representation of floating point-precision images have been reported so far (for example, refer to Non-patent Document 1 and Non-patent Document 2). For example, Patent Document 1 proposes a two-stage encoding method by which tone mapping is performed to create a low-bit depth image and a difference between the decoded image and the original image is encoded by another coder. In addition, Patent Document 2 discusses application of Lloyd-Max quantization instead of tone mapping to reduce the bit rate at the time of lossy compression.